1. Field of the Invention
The present invention relates to a semiconductor light-emitting device, and more particularly, to a semiconductor light-emitting device with high light-extraction efficiency.
2. Description of the Prior Art
The current semiconductor light-emitting devices, such as light-emitting diodes, have been used for a wide variety of applications, e.g. illumination, remote control. To ensure high functional reliability as great as possible and a low power requirement of the semiconductor light-emitting devices, the external quantum efficiency is required for the devices.
In principle, the external quantum efficiency of a semiconductor light-emitting device is determined both by the internal quantum efficiency and extraction efficiency. The internal quantum efficiency is determined by the material property and quality. The extraction efficiency refers to the proportion of radiation emitted from the interior of the device into surrounding air or encapsulating epoxy. The extraction efficiency is determined by the losses occurred when radiation leaves the interior of the device. One of the main causes for such losses is the radiation proportion resulted from the high optical refraction coefficient of the semiconductor material, e.g. about 3.6 for gallium arsenide (GaAs), that cannot be emitted outside at the semiconductor surface on account of total reflection.
Regarding the manufacturing processes of semiconductor light-emitting devices in the prior art, e.g. U.S. Pat. No. 6,277,665, it disclosed a surface roughening method to enhance the external quantum efficiency of a semiconductor light-emitting device. According to the semiconductor light-emitting device in the patent, the exposed portion of its top-most layer exhibits a textured surface morphology, and thereby the external quantum efficiency of the semiconductor light-emitting device is enhanced.
Currently, the scope of a light-emitting diode is designed to be a straight type. If the scope, i.e. the sidewall, of the light-emitting diode forms a regular or an irregular surface morphology, the light-extraction area of the sidewall will be increased to enhance the light-extraction efficiency and the external quantum efficiency of the semiconductor light-emitting device.
Therefore, the main scope of the invention is to provide a semiconductor light-emitting device with a sidewall exhibiting a surface morphology. Thereby, the light-emitting area of the sidewall is increased to enhance the light-extraction efficiency of the semiconductor light-emitting device.